In the past, a coated tool obtained by forming a hard coating layer constituted of the following (a) and (b) on a surface of a substrate constituted of a tungsten carbide (hereinafter represented by WC)-based cemented carbide (hereinafter referred to as tool substrate) has generally been known:
(a) a Ti compound layer having a total average layer thickness in a range of 3 μm to 20 μm and consisting of two or more layers of a Ti carbide (hereinafter represented by TiC) layer, a Ti nitride (hereinafter, similarly, represented by TiN) layer, a Ti carbonitride (hereinafter represented by TiCN) layer, a Ti carboxide (hereinafter represented by TiCO) layer and a Ti carbon-nitrogen oxide (hereinafter represented by TiCNO) layer all of which are chemically deposited as a lower layer, and
(b) a chemically-deposited aluminum oxide (hereinafter represented by Al2O3) layer having an average layer thickness in a range of 1 μm to 15 μm as an upper layer, and
it has also been known that a coated tool coated with the above-described hard coating layer exhibits excellent wear resistance.
In addition, a variety of studies have been conducted to further improve a variety of cutting performances required for a cutting tool, and, for example, to improve the plastic deformation resistance, high toughness and wear resistance of a coated tool, as described in JP-A-2009-28894, a coated tool has been proposed in which a surface of a tool substrate is coated with a Ti compound layer and an Al2O3 layer, and regarding the texture coefficient TC of the Al2O3 layer, the TC(006) is set to be larger than 2, and furthermore, the second largest texture coefficient TC(104) is set to satisfy 2>TC(104)>0.5.
However, with the above-described coated tool, while the wear resistance of the coat improved, there was a problem of poor chipping resistance and fracture resistance.
In addition, as described in JP-A-H11-140647, a coated tool has been proposed as well in which a surface of a tool substrate is coated with a Ti compound layer and an Al2O3 layer, and regarding the texture coefficient TC of the Al2O3 layer, TC(104) and TC(110) are set to be larger than 1.2.
Furthermore, as described in WO 2006/064724-A, a coated tool has been proposed as well in which a surface of a tool substrate is coated with a TiCN layer and an Al2O3 layer, the TiCN layer has tensile stress S1, the Al2O3 layer has compressive stress S2, and the tensile stress S1 and the compressive stress S2 are set to satisfy a relationship of400 MPa≦|S2−S1|≦3500 MPa,
thereby procuring both toughness and wear resistance.